Make ClusterTemplate.IDMSRef functional for HyperShift. Read and validate the referenced ConfigMap, convert the configured mirror mappings to HostedCluster.spec.imageContentSources, and add success, missing-reference, and malformed-input tests.\n\nCurrent stub: internal/resources/hypershift.go
Make ClusterTemplate.IDMSRef functional for HyperShift. Read and validate the referenced ConfigMap, convert the configured mirror mappings to HostedCluster.spec.imageContentSources, and add success, missing-reference, and malformed-input tests.\n\nCurrent stub: internal/resources/hypershift.go